Buoyant Force and Archimedes

Buoyant Force

Archimedes' Principle

What is a buoyant force?

A buoyant force is an upward force exerted on an object by a fluid.

A floating object experiences a greater buoyant force than its own weight.

Multiple Choice

What is a buoyant force?

• The force that makes an object sink

• The density of the fluid an object is submerged.

• An upward force exerted on an object by a fluid.

• The depth to which an object is submerged in a fluid.

Multiple Choice

What will happen if the buoyant force is greater than the object's weight (gravity)?

• The object will sink

• The object will float

• The object will get wet

• The object will be under the surface of the fluid but will not touch the bottom.

Multiple Choice

What will happen if the buoyant force is lower than the object's weight (gravity)?

• The object will sink

• The object will float

• The object will get wet

• The object will be under the surface of the fluid but will not touch the bottom.

The magnitude of the buoyant force (F_B) will depend of the density of the fluid (ρ_f) and the displaced volume of the fluid (V_f).

Multiple Choice

What does this symbol ρ_f represent?

• density of the object

• pressure of the fluid

• density of the fluid

• weight of the fluid

Multiple Choice

What does this symbol V_f represent?

• displaced volume of the fluid

• volume of the object

• velocity of the fluid

• weight of the fluid

Multiple Choice

What does this symbol g represent?

• weight of the object

• gravity's acceleration

• force of gravity

• shape of the object

Multiple Choice

If we put an object in a container with water and it sinks. Would we have the same result if we put it in a container with honey?

• Yes, because the object weights too much

• Yes, because the object is probably too big

• No, because the density of honey is greater. The object might float.

• There's no way to know.

Multiple Choice

What will happen if a solid object immersed in a fluid weighs more than the weight of the fluid it displaces?

• The object will rise to the surface

• The object will be neutrally buoyant

• The object will move up and down in the fluid.

• The object will sink to the bottom

Multiple Choice

The materials used to make a steel ship have a density greater than water.  How is it possible that a ship floats in water?

• Helium and hydrogen is mixed with the steel

• The steel is made of many layers pressed together rather than solid sheets of steel

• Steel ships are shaped to displace an amount of water with a weight that is greater than the weight of the ship

• The steel is raised to a high heat first to make it less dense before it is solidified for shipbuilding